improve the robustness of ndncert library

Change-Id: Iaabc4d8f28ca27a7e7f501ebd122c5231ceb3ac0
diff --git a/tests/unit-tests/client-config.t.cpp b/tests/unit-tests/client-config.t.cpp
index 5d662ff..0f8aa95 100644
--- a/tests/unit-tests/client-config.t.cpp
+++ b/tests/unit-tests/client-config.t.cpp
@@ -44,6 +44,24 @@
   BOOST_CHECK_EQUAL(config.m_localNdncertAnchor, "/usr/local/etc/ndncert/anchor.key");
 }
 
+BOOST_AUTO_TEST_CASE(ReadNonexistConfigFile)
+{
+  ClientConfig config;
+  BOOST_CHECK_THROW(config.load("tests/unit-tests/nonexist"), ClientConfig::Error);
+}
+
+BOOST_AUTO_TEST_CASE(ReadConfigFileWithInvalidCert)
+{
+  ClientConfig config;
+  BOOST_CHECK_THROW(config.load("tests/unit-tests/client.conf.test2"), ClientConfig::Error);
+}
+
+BOOST_AUTO_TEST_CASE(ReadConfigFileWithoutCaPrefix)
+{
+  ClientConfig config;
+  BOOST_CHECK_THROW(config.load("tests/unit-tests/client.conf.test3"), ClientConfig::Error);
+}
+
 BOOST_AUTO_TEST_CASE(AddAndRemoveCaItem)
 {
   ClientConfig config;